Method for treating coal

Abstract

A method of treating coal. The method comprises passing the coal through a retort having a shell temperature of about 500°-1000° F. and shock heating the coal to a maximum surface temperature of about 500°-1000° F. without allowing the coal to become exothermic. The coal is prevented from going exothermic by a combination of factors, including the evaporation of moisture from the shock heated coal, the tendency of coal to absorb heat and maintain a temperature of about 390°-570° F. until the coal undergoes molecular transformation of complex hydrocarbons contained in the coal to simpler forms, and the effects of a cooling blanket gas passed through the shock heated coal. The blanket gas preferably comprises an oxygen lean blanket gas stream containing about 2-8% oxygen by volume. The treated coal exhibits extremely low moisture content and increased BTU value and other improved combustion characteristics.

I claim: 
     
       1. A method for continuously treating moisture-containing coal in order to increase the rank of said coal, without allowing said coal to become exothermic, comprising the steps of: a. passing said coal through externally heated retort means having an external shell temperature of about 500°-1,000° F.;   b. shock heating said coal in the drying section of said retort means, thereby driving off said moisture from said coal such that said coal contains about 1% or less by weight moisture and generating CO 2 , wherein said CO 2  is absorbed by the interstices of said coal replacing said moisture driven off from said coal to thereby resist reabsorption of water by said coal following pretreatment;   c. treating said shock heated dried coal in the treating section of said retort means wherein said treated coal maintains an internal temperature of about 350°-550° F. and before said coal becomes exothermic, and before vaporization of volatiles from said coal occurs, passing a cooling oxygen lean blanket gas stream having a temperature of about 300°-450° F. into said retort and through said shock heated dried coal until said coal surface is cooled, by providing said blanket gas with sufficient oxygen to catalyze molecular simplification of hydrocarbon molecules in said coal without allowing said coal to become exothermic; and   d. recovering said treated coal from said retort means.   
     
     
       2. The method of claim 1 wherein said retort means is heated by hot gas or flame. 
     
     
       3. The method of claim 1 wherein said blanket gas is passed through said shock heated coal in a direction countercurrent to the direction of said coal passing through said retort means. 
     
     
       4. The method of claim 1 wherein said oxygen content of said blanket gas entering said retort is monitored and controlled by gas monitoring and control means and maintained at about a 2-8% oxygen concentration by volume of said blanket gas entering said retort means by said gas monitoring and control means. 
     
     
       5. The method of claim 4 wherein said gas monitoring and control means continuously monitors said blanket gas. 
     
     
       6. The method of claim 4 wherein said retort comprises an inclined rotary retort. 
     
     
       7. The method of claim 1 wherein said blanket gas comprises a mixture of oxygen and combustion gases. 
     
     
       8. The method of claim 1 wherein said blanket gas comprises a mixture of oxygen and nitrogen. 
     
     
       9. The method of claim 1 wherein said coal contains up to about 50% by weight moisture prior to said treating, and said treating. 
     
     
       10. The method of claim 1 wherein said retort comprises an inclined horizontal flighted cylindrical retort and said shell is heated on the lower 1/12 quadrant on the descending side of said retort. 
     
     
       11. The method of claim 1 wherein said coal has a particle size of about 2" maximum ×0". 
     
     
       12. The method of claim 1 wherein -30 mesh coal is removed prior to said treating of said coal. 
     
     
       13. The method of claim 1 wherein said retort comprises a vertical retort.